Moldings made with use of polypropylenes (propylene homopolymer, ethylene-propylene copolymer, ethylene-propylene block copolymer) are relatively superior in an economical efficiency and have been used for wide fields. However, moldings made with use of propylene homopolymer have a high rigidity but have a disadvantage of a poor impact resistance, particularly a poor impact resistance at a low temperature. Thus, there have been hitherto made many propositions in order to improve an impact resistance at a low temperature.
In those propositions, propylene type block copolymers have been prepared generally by forming at first homopolymer components and then introducing ethylene-propylene random copolymer components. Since moldings made with use of propylene type block copolymers are superior in an impact resistance at a low temperature, they are used widely in various industrial fields such as automobiles and household electric appliances.
However, moldings made with use of conventional propylene type block copolymers are superior in an impact resistance but they have no transparency, thus they have such a disadvantage that they are not colored well when various pigments being added and they have such an additional disadvantage that a dimensional stability is bad.